Estes Trajector Rocksim

[Faroutspacenut]

Hi everyone,

Quick intro: recent Born Again and thrilled to be back in the hobby. Took my kids to a local launch a couple of months ago and now I'm totally hooked.

I picked up several kits at the Estes sale, the PSII Trajector among them. I'm planning to launch it tomorrow on a F15-6 for its maiden flight but Thurstcurve fails the engine as too slow off the pad. Would like to confirm with Rocksim but the only rocksim file I can find (https://www.rocketreviews.com/rocksim-estes---trajector.html) is crashing the program when I try to "prepare for launch". Could someone please help me by trying out this file and seeing if it does the same thing to you? Or perhaps one of you you has a .rkt file that's working?

One minor complication for me: It's a very sloppy build I'm ashamed to admit (I plead kid participation as the reason, ahem) and the motor mount tube is a VERY tight fit thanks to some rogue adhesive I can't quite sand flat. I put an engine in to test the fit and it's not coming out without some mechanical assistance (aka pliers). I don't want to risk cracking the clay nozzle, so my plan is just to leave it in until after it launches... assuming this engine sims successfully (and safely). If not I'll yank it and just bin the engine.

Thanks in advance for your help. I've been reading these forums every night and am learning tons.

 

[5x7]

It's one of the recommended motors and plenty have been flown with it. Just make sure you are using the pro series pad or something equivalent and avoid high winds.

 

[dhkaiser]

Thrustcurve does not like anything less than 50ft/s off the rod. What was it's reported speed? My Estes Mammoth fails with 42ft/s off the rail with a F15 motor. Flies fine.

 

[Scott_650]

My Trajector came out slightly heavier than Estes estimated weight - plenty of JB Weld did it I suppose, only epoxy I had handy, and it flies great on that motor.

 

[Faroutspacenut]

Thrustcurve does not like anything less than 50ft/s off the rod. What was it's reported speed? My Estes Mammoth fails with 42ft/s off the rail with a F15 motor. Flies fine.

It's telling me 43 ft/sec, so looks like I'll be in good shape. Thanks.

 

[Faroutspacenut]

For those keeping score... It was a great flight. 889 feet on the Estes altimeter I had clipped to the nosecone.

 

[TangoJuliet]

Good to hear. I've got one in primer right now preparing for paint (hopefully next week when I'm home again), and I suspect mine will also be slightly heavier than stock as I'm planning a non-stock paint scheme that may add some nominal weight.

 

[Faroutspacenut]

Here is some footage of the flight, followed immediately by our Estes Mammoth on the same F15-6 engine. That one, as you'll hear the LCO announce, was "right on the money".

[video=vimeo;208696226]https://vimeo.com/208696226[/video]

 

[TangoJuliet]

No video link.

 

[Faroutspacenut]

that's strange. it's showing embedded right here in the reply when I look at this thread. Have never posted videos here so not sure why that is. here's the link: "https://vimeo.com/208696226"

 

[K'Tesh]

Hi Rob,

Welcome to TRF!

While I can't help you with .rkt files, I'm pretty decent at OpenRocket. I don't trust anything I find on rocketreviews, as the files there are notoriously inaccurate. Best thing to do is to create them yourself, or go with a trusted designer.

OpenRocket is free, opensource, and available for download here:
https://openrocket.sourceforge.net/download.html

All The Best!
Jim

 

[Todderbert]

that's strange. it's showing embedded right here in the reply when I look at this thread. Have never posted videos here so not sure why that is. here's the link: "https://vimeo.com/208696226"

Your embedded video is working for me.

 

[TangoJuliet]

It's probably an issue on my end. YouTube is blocked on our company server, and apparently, so is Vimeo. The link doesn't appear at all for me in your first post, and the link in your second post locks up TRF for me. Oh well, I'll just have to wait until I'm home next week to watch it.

 

[neil_w]

If I'm interpreting what I'm seeing on the video correctly, it looks like the 6 second delay was just about perfect for the Trajector (Estes recommends -6 or -8). On the other hand, Estes also says it should fly 1600 ft on an F15, and you're reporting less than 900 ft. Hmm.

 

[Faroutspacenut]

If I'm interpreting what I'm seeing on the video correctly, it looks like the 6 second delay was just about perfect for the Trajector (Estes recommends -6 or -8). On the other hand, Estes also says it should fly 1600 ft on an F15, and you're reporting less than 900 ft. Hmm.

Keep in mind that's based on my $25 estes altimeter so that or user error could be an explanation for the altitude. I've got a JLA3 on the way - will try it with that and same engine and see how it goes. The only rocksim file I can find for this model crashes my program (which started this thread in the first place) so having hard time modeling the flight otherwise. (I'd try making my own sim but those fins are tricky)

 

[dhkaiser]

Estes PSII altitude estimates have been VERY optimistic in my experience. Estes says my Mammoth on a F15 will reach 1600 ft. I have never gone much higher than 1000 ft on F15 motors.

 

[swatkat]

My Mammoth on the F15 is ~850 feet. Trajector is about 900. Trajector on a G40-10W is ~2700.

 

[TangoJuliet]

Trajector on a G40-10W is ~2700.

Are you using a JL Chute Release with that? I love the G40's and G80's in my MDRM, but I don't have a chute release... Yet!

 

[Bat-mite]

To expand on the "speed off the pad" thing a bit more, thrustcurve.org doesn't know your launch conditions and assumes a worst case scenario. In little to no wind, you can get away with less speed off the pad. That's because nothing is trying to knock your rocket over as it is building up its initial thrust.

If you look at the actual thrust curve of the Estes F15, it reaches peak thrust at one half-second. Peak thrust is 25 Newtons, so if you can keep the rocket on the guide for at least a half-second, you could potentially launch an 18-ounce rocket safely. So, a longer rod/rail is your friend for a slower burning motor.

 

[Faroutspacenut]

My Mammoth on the F15 is ~850 feet. Trajector is about 900. Trajector on a G40-10W is ~2700.

Thanks for the independent confirmation. That's pretty much exactly what mine did. Now I need to get one of those G40s!!!